What are the common Session and Cookie operations in PHP programming?

PHP is a server scripting language that is widely used in the field of Web development. In PHP programming, Session and Cookie are two important concepts used to maintain user status and track user behavior. This article will introduce common Session and Cookie operations in PHP programming, and how to use them to implement user authentication, data storage and other functions.

1. What are Session and Cookies?

Session and Cookie are both mechanisms in the HTTP protocol, used to maintain user status and record user behavior in web applications. Session is a server-side technology used to store and maintain the user's session state on the server; Cookie is a client-side technology used to store and transfer session data on the browser.

The main difference between Session and Cookie is storage location, usage and security. Session data is stored on the server side, which is relatively secure, but requires additional server resources and maintenance costs; while cookie data is stored on the client side, which facilitates data transfer and sharing, but there is a risk of tampering. Therefore, in specific applications, it is necessary to select appropriate technologies based on actual needs to maintain user status and track user behavior.

2. Session operation

1. Opening Session

Before using Session, you need to open Session, which can be achieved through the session_start() function. Only after the Session is opened can data be stored in the Session and Session data can be shared between different pages. The sample code is as follows:

<?php
session_start();
?>

2. Storing Session data

You can use the $_SESSION array to store and access Session data. When storing data, you only need to assign the data to the key value in the $_SESSION array. The sample code is as follows:

<?php
session_start();
$_SESSION['username'] = 'Tom';
$_SESSION['age'] = 22;
?>

3. Read Session data

Use the $_SESSION array to easily read Session data. You only need to access the corresponding data through key values. The sample code is as follows:

<?php
session_start();
echo $_SESSION['username']; // 输出Tom
echo $_SESSION['age']; // 输出22
?>

4. Delete Session data

Use the unset() function to delete the specified Session data. The sample code is as follows:

<?php
session_start();
unset($_SESSION['username']); // 删除username数据
?>

5. Destroy Session

Use the session_destroy() function to destroy the current Session and delete all associated data. The sample code is as follows:

<?php
session_start();
session_destroy(); // 销毁当前Session
?>

3. Cookie operation

1. Setting Cookie

You can use the setcookie() function to set Cookie. The setcookie() function accepts multiple parameters, among which the most commonly used parameters are cookie name, cookie value, cookie expiration time, etc. For example, the following code is used to set a cookie with a name of username, a value of Tom, and an expiration time of 1 hour:

<?php
setcookie('username', 'Tom', time()+3600); // 设置一个过期时间为1小时的Cookie
?>

2. Read Cookie

You can use $_COOKIE Variable to read the cookie data submitted by the client. You only need to access the corresponding data through key values. The sample code is as follows:

<?php
echo $_COOKIE['username']; // 输出Tom
?>

3. Modify Cookie

When modifying Cookie, you only need to call the setcookie() function again. The sample code is as follows:

<?php
setcookie('username', 'Jerry', time()+3600); // 修改Cookie的值为Jerry
?>

4. Delete Cookie

You can use the setcookie() function to set the Cookie expiration time to before the current time to achieve the effect of deleting Cookie. The sample code is as follows:

<?php
setcookie('username', '', time()-3600); // 将Cookie的过期时间设置为当前时间之前，从而使Cookie失效
?>

4. Summary

This article introduces the common Session and Cookie operations in PHP programming, and how to use them to implement user authentication, data storage and other functions. In practical applications, it is necessary to select appropriate technologies based on actual needs to maintain user status and track user behavior, and reasonably set the expiration time of Session and Cookie to ensure security.

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